The present disclosure relates to the field of objective quality measurement for packet based audio and video applications. Specifically, this disclosure describes embodiments of a system and method for diagnostic modeling of audio and video quality of service.
The quality of video or audio media can be measured either subjectively or objectively. Subjective measurements measure the perceptions and opinions of viewers or listeners. Objective measurements measure specific stream and/or transmission parameters. For subjective quality measurements, one person's impression of ‘good’ may be quite different to another person's impression, but neither is incorrect. Subjective quality measurement systems are therefore designed and tested against an “average” person's perception of audio or video quality and summarized by a Mean Opinion Score (“MOS”).
Subjective testing aims to find the average user's perception of the media quality that is delivered by a system by asking a panel of users a directed question and providing them with a limited response choice. For example, to determine the listening quality of a voice signal, users are asked to rate “the quality of the speech” on a five-point scale from Bad to Excellent (in accordance with ITU-T Recommendation P.800). The MOS for a particular test condition is calculated by averaging the votes of all subjects for that particular condition. A subjective test will typically contain many different conditions. Therefore, such tests take a long time to perform and the results are influenced by a wide range of factors.
Objective testing techniques measure physical properties of a system. Objective perceptual algorithms map these physical properties to a predicted subjective score. In comparison to subjective testing, objective measurements are fast, inexpensive and repeatable. Significant work has lead to objective prediction techniques that provide an automated prediction of audio and video quality and replace the need for a large proportion of subjective testing. Objective quality measurement techniques can be further categorized as intrusive (active) or non-intrusive (passive). In general, active methods rely on a known test signal being passed through the system being analyzed; passive methods monitor live traffic.